Scientific Method —

Alliant Techsystems surprises with a manned rocket

Commercial rocket and crew capsule will be made of pieces from other programs.

While it's widely known that Utah-based Alliant Techsystems (ATK) has been working on a new rocket, they managed to keep their spacecraft a secret until today. With their entry, there now are five companies competing to carry crew to the International Space Program: SpaceX, Boeing, Blue Origin, Sierra Nevada, and ATK.

The new system, called Liberty, was announced at an ATK press conference a short time ago. It uses a solid first stage from the Space Launch System, an Astrium liquid first stage from Ariane 5 as its second stage, and a brand-new composite crew capsule with a pusher-type Max Launch Abort System (MLAS) shrouding the capsule. ATK says they will attempt a first launch sometime in 2014.

Components

The ATK first stage is quite familiar: it's the five-segment Solid Rocket Booster from the Space Launch System (SLS). This was originally created from scratch for Constellation's Ares 1 rocket after using the Shuttle's SRB's turned out not to be technically feasible. It's had three successful ground firings.

One advantage of a solid rocket motor is that they're relatively cheap to manufacture. They can be tricky to use, though, and rating them for human launches requires some way to absorb the shock accelerations the motors experience as they burn. Unmitigated, the 5-6G shaking can be quite dangerous to human beings. NASA famously installed giant shock absorbers on the top and bottom of the Ares I.

ATK claims to have largely solved that problem. They didn't talk about the other disadvantage of a solid rocket motor, which is that they are devilishly difficult to turn off once started. The Ares/SLS rocket motors do not have that capability.

Astrium's Ariane 5 first stage will function as a second stage for the Liberty rocket. Astrium's John Schumacher pointed out that the liquid oxygen/hydrogen Vulcain 2-powered stage has had 47 successful launches and is considered to be quite reliable. The stage will need to be considerably strengthened to ride atop the solid booster, and the Vulcain engine will need to be modified for air start. That's not generally an easy task, but according to Schumacher, Astrium has been working on it for quite some time. Although the stage is manufactured in Europe, eventually it will be made in the United States to cut costs.

Evidently ATK has licensed the design from NASA and has continued to develop it. ATK says the capsule will be good for ten launches with water landings.

The service module, which actually carries the crew to the International Space Station (or other destinations), is basically the 30,000-pound spacecraft that has been developed by Lockheed-Martin for the Orion space capsule. It won't be tested by LockMart until 2014, which also raises the question of which company will test it first. But it's a perfect fit for the Composite Crew Capsule, which was developed to match Orion's dimensions.

The Max Launch Abort System, or MLAS, is also an alternate design left over from the Constellation program. MLAS is kind of nifty in that it consists of four solid rockets attached to a shell that fits over the top of the crew capsule. In the event of an emergency, the four Terrier rockets ignite and carry the crew to a safe distance, whereupon the assembly pops a couple of parachutes to orient itself upright, and then (presumably) more parachutes to drop it to safety. That last part is interesting, again because the CCM was designed for water landings to match Orion. ATK says they're examining a way to bring it down on land, which they would have to do in the event of a pad abort.

The last portion of the announcement was that ATK would use the venerable Launch Pad 39B from NASA for testing, and plans to launch Liberty with an already-existing mobile launcher. ATK didn't say whether they would build their own platforms.

Market

One of the most surprising claims ATK's Kent Rominger made during the press conference was "great customer service." Those are unusual words coming from a defense contractor. ATK seems to realize that they have some skepticism to overcome.

Rominger spoke of having Liberty ready for crewed launches by 2015, fairly soon compared to their competitors. But it's plausible because they have re-purposed many existing components (which also keeps their development costs very low). Those costs won't be amortized into ATK's launch prices, giving them a big advantage. NASA is even paying to man-rate Liberty's SRB due to its role in Ares.

The announcement also mentioned markets: space tourism, developing nations that want a space program, International Space Station servicing, and commercial cargo. Liberty will reportedly take 44,500 pounds to LEO, almost twice what a Falcon 9 can throw. In short, Alliant Techsystems has surprised many of us with a formidable new entrant into the commercial launch market.

All while Neil Armstrong and Gene Cernan go on claiming that NASA should be the only game in town. Very interesting stuff, apparently ATK was also the manufacturer of the space shuttle's solid rocket boosters.

As an aside, would it be possible to provide metric figures as well in future for the sake of Ars' international readership?

Any idea how this compares to SpaceX's Falcon Heavy? From what I can tell the Heavy is rated for more payload & is scheduled for a flight test a year earlier, but I haven't heard much about it in the news recently. Also, not sure how compatibility with the CCM plays into the equation?

"rating them for human launches requires some way to absorb the shock accelerations the motors experience as they burn. Unmitigated, the 5-6G shaking can be quite dangerous to human beings. "

Is this due to uneven burning? It suggests acoustic waves that could be damped by transducers introducing cancelling waveforms through the propellant. They don't have to be powerful enough to damp the acceleration, just smooth the burn rate/front.

It's a fair bet they haven't solved the shaking problem, since this was the critical problem during the earlier project and they seem to say "largely" solved so it remains at least partly.

tgoldman wrote:

Is this due to uneven burning? It suggests acoustic waves that could be damped by transducers introducing cancelling waveforms through the propellant. They don't have to be powerful enough to damp the acceleration, just smooth the burn rate/front.

"The concern isn't the shaking on the first stage, but how it affects everything that sits on top: the Orion crew capsule, instrument unit, and a booster.

That first stage is composed of five segments derived from the solid rocket boosters that NASA uses to launch the shuttle and would be built by ATK Launch Systems of Brigham City, Utah.

The shaking problem, which is common to solid rocket boosters, involves pulses of added acceleration caused by gas vortices in the rocket similar to the wake that develops behind a fast-moving boat, said Arenas, who has researched vibration and space-launch issues.

Those vortices happen to match the natural vibrating frequencies of the motor's combustion chamber, and the combination causes the shaking.

Senior managers were told of the findings last fall, but NASA did not talk about them publicly until the AP filed a Freedom of Information Act request earlier this month and the watchdog Web site NASAwatch.com submitted detailed engineering-oriented questions.

The response to those questions, given to both NASAwatch and AP, were shared with outside experts, who judged it a serious problem.

NASA engineers characterized the shaking as being in what the agency considers the "red zone" of risk, ranking a five on a 1-to-5 scale of severity.

"It's highly likely to happen and if it does, it's a disaster," said Fischbeck, an expert in engineering risks."

Essentially a solid candle engine is an organ pipe that makes a tremendous sound as it is slowly hollowed out. I don't know if you can set up sufficiently powerful and controlled pulsations that they cancel the dynamically evolving and inherently chaotic forcing that vortices would set up in the sound pipe.

The easiest way to get rid of the problem would be to go to a short engine, i.e. some form of fuel powder/ball fed engine. And by then it is likely simpler to use a liquid fuel engine.

"Essentially a solid candle engine is an organ pipe that makes a tremendous sound as it is slowly hollowed out. I don't know if you can set up sufficiently powerful and controlled pulsations that they cancel the dynamically evolving and inherently chaotic forcing that vortices would set up in the sound pipe."

"The easiest way to get rid of the problem would be to go to a short engine, i.e. some form of fuel powder/ball fed engine. And by then it is likely simpler to use a liquid fuel engine."

While it may not make sense to most observers, the people to talk to about possible engineering approaches to solve or mitigate these problems would be the Navy. [Although I do wonder how much is still classified as per Trident II missile mentioned above.]

It's a fair bet they haven't solved the shaking problem, since this was the critical problem during the earlier project and they seem to say "largely" solved so it remains at least partly.

..snip...

Essentially a solid candle engine is an organ pipe that makes a tremendous sound as it is slowly hollowed out. I don't know if you can set up sufficiently powerful and controlled pulsations that they cancel the dynamically evolving and inherently chaotic forcing that vortices would set up in the sound pipe.

The easiest way to get rid of the problem would be to go to a short engine, i.e. some form of fuel powder/ball fed engine. And by then it is likely simpler to use a liquid fuel engine.